This invention relates generally to a rotating disk data storage apparatus, particularly to a flexible magnetic disk drive (FDD) for use as a peripheral, and more particularly to such a device to be coupled to a processor, as typified by a personal computer (PC), by way of what are known to the specialists as universal serial buses (USB). Still more particularly, the invention deals with how to save greater power consumed by such a device, particularly by disk sensor means customarily incorporated therein, in response to a power saving signal, sometimes referred to as suspend/resume signal, that is fed from the processor.
FDDs in general are equipped with a disk sensor in order to inform the PC with which they are interfaced, of whether a disk is positioned on the turntable or not, as well as of whether a change has been made from one disk to another. U.S. Pat. No. 5,400,190 to Miura, dated Mar. 21, 1995 and assigned to the assignee of the instant application, is hereby cited as teaching a power saving system for the disk sensor.
The disk sensor as disclosed in this U.S. patent is a serial connection of a mechanical sensor switch and a pullup resistor. The sensor switch is held closed when a disk is not loaded on the turntable, holding the disk sensor output high, and opened when a disk is, making the disk sensor output go low.
Particularly in computer systems where two or more FDDs are connected to one computer, total power consumption by the disk sensors of all such peripherals is by no means negligible. The computer itself has indeed been designed for reduction of power consumed by FDDs in consideration of this mode of use, as manifested by so-called suspend/resume signals fed from the computer to the FDDs in order to avoid waste of power. The suspend/resume signal has a xe2x80x9csuspendxe2x80x9d state during which the FDD needs not be active and so may be held unpowered, and a xe2x80x9cresumexe2x80x9d state during which the FDD must be powered. The suspend/resume signal is therefore a power-saving signal, its xe2x80x9csuspendxe2x80x9d state representing a power-saving period, and its xe2x80x9cresumexe2x80x9d state a non-power-saving period. The suspend/resume signal will be sometimes referred to as power-saving signal in this specification.
Difficulties had been experienced, however, in reduction of power consumed by the disk sensors, among other power-consuming components of the FDDs. When the suspend/resume signal gains a xe2x80x9cresumexe2x80x9d state, the FDDs must be able to inform the computer of not only whether a disk is then loaded or unloaded, but whether a disk change has been made during the preceding xe2x80x9csuspendxe2x80x9d state. For this reason the disk sensors had long had to be held powered regardless of whether the FDDs in which they were incorporated were active or inactive.
U.S. Pat. No. 5,400,190, supra, represents a solution to this problem, teaching to connect the noted serial switch-resistor circuit of the disk sensor between an OR gate and ground. The sensor switch has its output fed back to the OR gate, to which is also supplied the power saving signal. Consequently, in the event of a disk change during a power saving period, the OR gate is held low, so that no current flows through the resistor.
This improved prior art disk sensor has proved to possess a shortcoming, particularly in applications where FDDs are USB interfaced with a PC. The FDD incorporating the prior art disk sensor has a flip-flop for memorizing, so to say, a disk change taking place when the FDD is inactive. The flip-flop maintains its state upon disk withdrawal until reset by a stepping pulse applied to the stepper motor for track seeking. Actually reset by a stepping pulse supplied upon resumption of FDD operation, the flip-flop puts out a signal indicative of a disk change. Thus, according to this prior art device, the PC was left uninformed of the disk change until appearance of the stepping pulses.
In most PC systems before the advent of the USB interfacing technology, the FDD controller (FDC) was built into the PC rather than into the FDD. The operating system of the PC has direct access to the FDC in this case, so that little or no inconvenience occurred as a result of the slight time lag between appearance of stepping pulses and reception of the disk change signal. However, when an FDD is USB interfaced with a PC, as has been an ever-growing trend in recent years, the FDC is included in the interface circuit that is built into the FDD, enabling the computer to be informed of the conditions of the FDC in real time.
The present invention seeks, in an FDD or like rotating disk data storage apparatus to be interfaced with a PC or like processor as a peripheral, to reduce waste of power by the disk sensor customarily incorporated in such apparatus and, at the same time, to let the processor know as quickly as possible a disk change that has occurred while the peripheral is inactive.
Briefly, the invention may be summarized as a rotating disk data storage system operating under the control of a processor, and comprising a data storage device and an interface. The data storage device includes disk sensor means for providing an output signal indicative of whether a data storage disk is in the device or not. The interface comprises power-saving means for generating a power-saving signal, such as the standard SUSPEND/RESUME signal, under the direction of the processor, the power-saving signal having a power-saving state, indicative of the fact that the data storage device is in a power-saving state, and a non-power-saving state indicative of the fact that the data storage device is not in a power-saving state. Also included in the interface are sampling means and disk status means. The sampling means samples the output signal of the disk sensor at three different moments that are predetermined in relation to each power-saving period of the power-saving signal. The disk status means ascertains a history of disk loading and unloading past each power-saving state of the power-saving signal on the basis of the three latest samples of the output signal of the disk sensor means.
In a preferred embodiment the disk sensor means is per se of the known type, producing an output signal that is correctly representative of disk presence or absence both when the power-saving signal is in the non-power-saving state and as long as no disk change is made during the power-saving state of the power-saving signal, but that, in the event of a change from one disk to another during the power-saving state of the power-saving signal, remains indicative of disk absence from the moment said one disk was unloaded to, at the earliest, the moment the power-saving signal subsequently gains a non-power-saving state.
Thus, preferably, the three sampling moments in question are approximately the beginning and end of each power-saving state, and very shortly after the beginning of the following non-power-saving state, of the power-saving signal. For example when all the three disk sensor output samples represent disk presence, the disk status means determines that the disk has been left loaded throughout the power-saving state. If, however, a disk was unloaded, and another loaded subsequently, during the power-saving period, then the first and the third samples will indicate disk presence, and the second sample disk absence.
The disk status means may include a memory for storing a disk status datum representative of such a disk loading and unloading history ascertained as above from the latest set of three disk sensor output samples. Constantly renewed with each power-saving state of the power-saving signal, the disk status datum is to be delivered to the processor on demand therefrom. It is to be appreciated that the third sampling moment comes earlier than the appearance of stepping pulses, so that the disk status datum is deliverable to the processor almost immediately upon resumption of the non-power-saving state.
The above and other objects, features and advantages of the invention and the manner of realizing them will become more apparent, and the invention itself will best be understood, from the following description taken together with the attached drawings showing the preferred embodiments of the invention.